It is well known that inflation valves are typically employed to provide for ingress of air pressure into a sealed unit such as a tire or the like. It is also well known that overpressure plugs may be employed for safety purposes to assure that the inflation of the tire on the wheel does not exceed prescribed limits. Indeed, the use of overpressure plugs on aircraft wheels has, in recent years, become the norm.
Presently, the use of overpressure plugs requires that two orifices be provided in the tire wheel. A first orifice is employed for the inflation valve, while a second orifice receives the overpressure plug. As a consequence, existing wheels which have but a single orifice (intended for receipt of an inflation valve) are not adapted to readily receive an overpressure plug. In order to adapt such existing wheels to receive both an inflation valve and an overpressure plug, the wheels must be taken out of service and re-machined to provide the additional orifice. Moreover, even those wheels which are presently being manufactured require the additional cost of adding a second orifice to the wheel for the receipt of an over-inflation plug.
Presently, it is known to employ an inflation valve which includes overpressure relief. However, the techniques and structures presently employed rely upon the use of spring loaded devices to regulate the relief pressure flow. The reliability and cost of these structures has not proven to be sufficient to achieve wide spread use by the airlines. Accordingly, in order to achieve the highest degree of reliability, it appears to still be necessary to separately include overpressure plugs and inflation valves. The presently employed overpressure plugs which have enjoyed the greatest amount of success are rupture disks which have been found to be rather precise devices having a pressure burst accuracy on the order of .+-.5%. A number of airlines have been using such rupture disks for several years. In light of the foregoing, there is a need in the art for an inflation valve which provides for over pressure protection in a single unit. Employing such a device, the wheels presently in use which have but a single orifice can be retrofitted to receive the enhancement. Moreover, newly manufactured wheels will still require but a single orifice, maintaining a high level of structural integrity, while reducing manufacturing expenses.